Originally Posted by
Lathais
So open the thing up, clean out the dust, maybe get a better case with some good airflow and some fans and replace your CPU Cooler.
What case do you have? Do you have an aftermarket CPU Cooler already or is it stock? How long ago did you install it? Sometimes after a few years the thermal paste can dry out and this causes overheating. Simply removing the cooler and replacing the paste can fix the issue. If you are going that far though, may as well get a better CPU Cooler and OC your system. You'll get more out of that then a new CPU.
Upgrading your CPU will see very little increase in performance, especially if you OC it. There's not a huge upgrade in it and it would eat you whole budget anyway. As for GPU, again, to get a noticeable increase, your looking at a R9 390 or a GTX 970 which is your whole budget, and it's not a huge increase there either. A GTX 960 may be a very slight increase, but probably not.